Plasmid for gene expression in pichia ciferrii and transformation method using the same

ABSTRACT

Expression cassettes for transforming  Pichia ciferrii  and their use are disclosed. The present invention relates to expression cassettes containing  Pichia ciferrii  ribosomal DNA fragment, CYH r  gene resistant to cycloheximide, and a desired gene. Expression cassette further comprising  Pichia ciferrii  GAPDH promoter gene which allows an increase in the expression of the desired gene also provided. Moreover, the present invention provides a process for producing tetraacetyl phytosphingosine using transformed  Pichia ciferrii  cells with the expression cassettes in a higher yield.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to expression cassettes for transforming Pichia ciferrii. More particularly, it relates to expression cassettes containing Pichia ciferrii ribosomal DNA fragment, CYH^(r) gene resistant to cycloheximide, and a desired gene, and to uses thereof.

2. Description of the Prior Art

Pichia ciferrii has been used to biologically desulfurize coals (Stevens et al., U.S. Pat. No. 4,851,350), to produce D-alpha-amino acids (Takelchi et al., U.S. Pat. No. 5,068,187), to produce (S)-1-phenyl-1,3-propandiol (Ajinomoto, JP 6-90789A) or to produce secondary alcohols by stereospecific ketone reduction (Merck, EP-300287). Further, it produces and secretes tetraacetyl phytosphingosine (TAPS) which is a precursor of ceramides (Barenholz et al., Biochem. Biophys. Acta, 248, 458, 1971; ibid, 306, 341, 1973).

Phytosphingosines including TAPS, like ceramides, show an activity of surface skin-protection and of preventing excessive water-loss and dry out of the skin, facilitating their uses in cosmetics. They can be obtained from various microorganisms and easily converted to ceramides by N-acylation.

TAPS productions by wild type Pichia ciferrii ATCC 14091 and F-60-10 (NRRL 1301) are not satisfactory for commercial uses. To improve the production of TAPS in the strains of Pichia ciferrii, attempts to provide mutants which are capable of producing a higher level of TAPS have been made (Wickerham & Burton, J. Bacteriol., 80, 484, 1960; U.S. Pat. No. 5,618,706). The present inventors also developed novel useful mutant (KFCC-10937) which allows a larger amount of TAPS production in a shorter time (KR 98-49305A).

Pichia ciferrii had been classified into genus Hansenula and is recently reclassified into genus Pichia by 5S-RNA analysis (Yamada et al., Biosci, Biotechnol. Biochem., 58, 1245, 1994). By this reason, the genetic study of the Pichia yeasts is not sufficient and transformation method of Pichia ciferrii has not been established.

The present invention provides plasmid prACL2 comprising Pichia ciferrii serine palmitoyl transferase gene and a transformed Pichia ciferrii cell which allows an improved production of TAPS.

The inventors found that the known transformation method for Candida utilis (Kondo et al., J. Bacteriol., 177, 7171, 1995) can be modified and applied to the Pichia ciferrii. They cloned Pichia ciferrii ribosomal protein L41-coding gene to determine its nucleotide sequence and manipulated to give a resistance to cycloheximide, an antibiotic from yeasts, so as to be used as a selection marker. Thus recombinant gene may be linked to a plasmid which carry a desired gene to give an expression cassette which is useful to transform Pichia ciferrii in which the desired gene is expressed.

Moreover, the inventors succeeded in cloning of Pichia ciferrii GAPDH promoter gene and found that its insertion into the expression cassette allows an unexpected improvement of the expression level. In fact, they increased the production amount of TAPS by transforming the strain of Pichia ciferrii with the expression cassette carrying LCB2 gene as a desired gene and culturing the resulting transformed cells. LCB2 gene codes for palmitoyl transferase which is involved in the TAPS synthesis in the living body.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to determine and use genetic information of Pichia ciferrii ribosomal protein L41 gene.

Another object of the present invention is to provide an expression cassette for transforming Pichia ciferrii, which comprises Pichia ciferrii ribosomal DNA, Pichia ciferrii L41 gene as a selection marker, and a desired gene. In one preferred embodiment of the present invention, the marker is a gene conferring resistance to an antibiotic cycloheximide.

Another object of the present invention is to provide a method for transforming Pichia ciferrii with a plasmid containing the expression cassette.

The present invention determines and uses genetic information of Pichia ciferrii glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene and GAPDH promoter gene.

The present invention provides an expression cassette for transforming Pichia ciferrii, which comprises Pichia ciferrii ribosomal DNA, Pichia ciferrii L41 gene as a selection marker, Pichia ciferrii GAPDH promoter gene and a desired gene. In one preferred embodiment of the present invention, the marker is a gene conferring resistance to an antibiotic cycloheximide.

The present invention further provides an expression cassette for transforming Pichia ciferrii, which comprises Pichia ciferrii ribosomal DNA, Pichia ciferrii L41 gene as a selection marker, Pichia ciferrii GAPDH promoter gene, a desired gene and Pichia ciferrii ribosomal DNA. In one preferred embodiment of the present invention, the marker is a gene conferring resistance to an antibiotic cycloheximide.

The present invention determines and uses genetic information of Pichia ciferrii serine palmitoyl transferase which is involved in TAPS synthesis.

The present invention provides plasmid prACL2 comprising an expression cassette having Pichia ciferrii serine palmitoyl transferase gene and a transformed Pichia ciferrii cell with an improved production of TAPS.

The present invention further provides plasmid prACGL2 comprising an expression cassette having Pichia ciferrii serine palmitoyl transferase gene and a Pichia ciferrii transformant with an improved production of TAPS.

The present invention further provides plasmid prHECGL2 comprising an expression cassette having Pichia ciferrii serine palmitoyl transferase gene and a Pichia ciferrii transformant with an improved production of TAPS.

The present invention still further provides a method for producing TAPS by culturing the transformed Pichia ciferrii cells.

The objects mentioned above, other features and applications of the present invention would be much more apparent by those of ordinary skills in the art from the following explanation in detail.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a restriction map of various plasmids having Pichia ciferrii ribosomal DNA incorporated with L41 genes of Pichia ciferrii at different sites for each plasmid, in which

hatched boxes indicate ribosomal DNA fragments;

restriction enzymes in bold letters indicate the enzymes used for linearization of the respective plasmids;

arrows indicate the transcription direction of the genes; and

plasmid prACL2 carries LCB2 gene coding for serine palmitoyl transferase from Pichia ciferrii.

FIG. 2 is a restriction map of Pichia ciferrii LCB2 gene, and the orientation and the length of the arrows indicate the direction and degree of nucleotide sequencing, respectively.

FIG. 3 represents the construction and restriction map of plasmid prACL2.

FIG. 4 is a restriction map of Pichia ciferrii GAPDH gene, and the orientation and the length of the arrows indicate the direction and degree of nucleotide sequencing, respectively.

FIG. 5 represents the construction and restriction map of plasmid prACGL2.

FIG. 6 represents the construction and restriction map of plasmid prHECGL2.

FIGS. 7A-7D show the results of Southern blot analysis carried out to measure the copy number of LCB2 gene transformed into host cell.

DETAILED EXPLANATION OF THE INVENTION

Kondo et al describes a transformation method for Candida utilis in which an antibiotic resistant gene from yeast is used as a marker gene instead of the conventional bacterial one (Kondo et al., J. Bacteriol., 177, 7171, 1995). The present inventors made attempts to apply such an idea to Pichia ciferrii.

For this purpose, they cloned Pichia ciferrii ribosomal protein L41 gene and determined its nucleotide sequence. Further, they identified 56th amino acid which is responsible for the sensitivity to cycloheximide is proline and replaced it by glutamine to give cycloheximide-resistance to L41 protein. In the present invention, L41 gene is used as a selection marker.

1. Isolation of Pichia ciferrii Ribosomal Protein L41 Gene

By following and modifying the method by Kondo et at (Kondo et al., J. Bacteriol., 177, 7171, 1995), two primers CYH1 and CYH4 were synthesized.

CYH1: 5′-CGC GTA GTT AAY GTN CCN AAR AC-3′

CYH4: 5′-GCC TGG CCY TTY TGY TTY TTN TC-3′

The two primers are also represented as SEQ. ID. NO; 7 and SEQ. ID. NO. 8, respectively in SEQUENCE LISTING.

PCR was performed using the two primers to isolate Pichia ciferrii ribosomal protein L41 gene of about 300 bp, which was labeled to be used as a probe.

Thus obtained probe was used to carry out Southern blot analysis for Pichia ciferrii genome DNA. A genome DNA digested with EcoRI gives a desired band at 1.9 kb. EcoRI-digested DNA fragments of 1.9 kb was collected and used to construct pCYH1.9 which is used for nucleotide sequencing. The results are shown in FIG. 1. DNA sequence of Pichia ciferrii ATCC 14091 ribosomal protein L41 gene was to submitted on Mar. 7, 1998 to GenBank under accession number AF 053457. Pichia ciferrii ATCC 14091 ribosomal protein L41 gene has 737 base pairs including 419 bp intron. The putative amino acid sequence deduced from the nucleotide sequence shows a homology of 90% or more to those of other yeasts. It was also identified that the cycloheximide-sensitive amino acid is amino acid 56, proline.

2. Impartation of Cycloheximide Resistance to L41 Gene Construction of Plasmid PCYH1.9^(r) for Use in the Selection of Transformed Cell.

Site-directed mutagenesis was carried out to replace proline (aa 56) in L41 gene with glutamine in order to impart cycloheximide resistance to L41 gene. Thus obtained gene-manpulated gene is designated as ‘plasmid CYH1.9^(r)’.

Hereinafter, the L41 gene is indicated by an abbreviation of ‘CYH’ and the cycloheximide-resistant L41 gene is indicated by ‘CYH^(r)’ throughout the description.

3. Isolation of Pichia ciferrii Ribosomal DNA: Construction of Plasmid prDX9.0 for Improving Integration Efficiency of Desired Gene Into Chromosome

In order to improve the efficiency of integration of the desired gene into the chromosomal DNA, ribosomal DNA was employed. Within the cell, several hundred copies of ribosomal DNA occur.

PCR primers were synthesized by using the partial nucleotide sequence of Pichia ciferrii ribosomal RNA (Yamada et al., Biosci. Biotechnol. Biochem., 58, 1245, 1994). PCR of Pichia ciferrii ATCC 14091 genome DNA was carried out by using the primers to isolate ribosomal DNA fragment of 6.0 kb. The fragment was used as a probe for Southern blot analysis to isolate Pichia ciferrii ATCC 14091 ribosomal DNA fragment of 9 kb, which is inserted into plasmid pBluescript KS+ to produce plasmid prDX9.0.

Partial sequence of the ribosomal DNA fragment (9 kb) was determined, and the location and orientation of 5S, 26S, 5.8S and 18S ribosomal protein genes are shown in FIG. 1.

4. Construction of Recombinant Plasmids

Ribosomal DNA was digested with various restriction enzymes and ligated to CYH^(r) to give various plasmids as shown in FIG. 1 which will be analyzed for transformation efficiency in regard with (1) the transcription directions of respective genes; (2) the arrangement of ribosomal DNA and CYH^(r) gene; and (3) the kind of insertion site, ribosomal RNA structural gene or non-transcribed region.

The characteristics of the plasmid in FIG. 1 are summarized in Table 1.

TABLE 1 Plasmid Characteristics prXHNC Ribosomal DNA (3.5 kb) obtained by XbaI digestion is treated with HpaI/NcoI to remove 1.6 kb ribosomal DNA and then ligated to CYH^(r). prEHC Ribosomal DNA (3.8 kb) obtained by EcoRI digestion is treated with HpaI to remove 2 kb ribosomal DNA and then ligated to CYH^(r). prCEX CYH^(r) is ligated to EcoRI site of 1.1 kb ribosomal DNA obtained by EcoRI/XbaI digestion prCRX CYH^(r) is ligated to EcoRV site of 1.3 kb ribosomal DNA obtained by EcoRV/XbaI digestion prXCH CYH^(r) is ligated to HpaI site of 3.5 kb ribosomal DNA obtained by XbaI digestion prXCE CYH^(r) is ligated to EcoRI site of 3.5 kb ribosomal DNA obtained by XbaI digestion prXHC1.9 CYH^(r) is ligated to EcoRI site of 1.6 kb ribosomal DNA obtained by XbaI/HindIII digestion prAC1.9 CYH^(r) is ligated to EcoRV site of 0.6 kb ribosomal DNA obtained by HindIII/EcoRV digestion prEC1.9 CYH^(r) is ligated to EcoRI site of 1.4 kb ribosomal DNA obtained by HindIII/EcoRI digestion prHEC1.9F CYH^(r) is ligated to EcoRV site of 1.4 kb ribosomal DNA obtained by HindIII/EcoRI digestion prHEC1.9R Same as prHEC 1.9F except that the insertion orientation of CYH^(r) is reversed

In the nomenclature of the plasmid, for example prAC, the letter ‘p’ indicates a plasmid, ‘r’ indicates that the plasmid has a ribosomal DNA, and ‘C’ means for ‘CYH^(r).’ The letters ‘A’ in prAC1.9 and ‘E’ in prEC1.9 indicate restriction enzymes used for liberalization by digesting the ribosomal DNA. In case of other plasmids, ‘X’ means XbaI, ‘E’ means EcoRI, ‘R’ means EcoRV, and ‘H’ means HindIII, respectively. Therefore, the plasmid containing these letters in their name comprise ribosomal DNA fragments digested with these respective restriction enzymes. Moreover, numerical number after C indicates the size (base pairs) of the L41 gene, while the letter ‘F’ or ‘R’ means the orientation of ribosomal DNA fragment and CYH^(r).

5. Transformation and Selection of Transformed Cells

The method described by Klass and Peter (Klass & Peter, Curr. Genet., 25, 305, 1994) is followed. That is to say, cells of Pichia ciferrii ATCC 14091 grown in YEPD medium to OD_(600 nm) of 1.5 were collected by centrifugation and mixed with the plasmid. Electroporation was performed at 500V, 50 μF and 800Ω so as to transform the cells with the plasmid and subjected to growth in YEPD solid medium to which cycloheximide was added to select transformed cells containing cycloheximide-resistant L41 gene(CYH^(r)).

The transformation efficiency is shown in Table 2 (Example 17). The data in Table 2 reveals that prHEC1.9F in which the non-transcribed region between 5S and 26S ribosomal RNA structural genes is used as an insertion site has the highest transformation efficiency. And, prHEC1.pR in which the transcription direction of 5S RNA gene is opposite to that of CYH^(r) shows significantly decreased transformation efficiency.

6. Analysis of Transformed Cells by Southern Blot Analysis

Genomic DNA was isolated from the transformed cells and the insertion patterns of CYH^(r) were analyzed by Southern blot analysis. As a result thereof, it was found that 4-5 copies of CYH^(r) were present in the chromosome of the transformed cells. This result indicates that the transformation of Pichia ciferrii with the expression cassette of the present invention optimizes the integration of the desired gene into the chromosome of transformed Pichia ciferrii cells.

7. Construction of prACL2 for TAPS Production; Transformation: and the Production of TAPS by Cultivation of Transformed Cells

An expression plasmid was constructed from an expression cassette comprising LCB2 gene for producing serine palmitoyl transferase and transformed into the mutant Pichia ciferrii KFCC-10937 to evaluate the TAPS production. The desired gene, LCB2 gene codes for serine palmitoyl transferase, which is involved in TAPS synthesis, and the mutant KFCC-10937 was developed by the inventors (KR 98-493 05A).

Serine palmitoyl transferase (3-ketosphinganine synthase, EC 2.3.1.50) is involved in the first step, which is the rate limiting step of the overall reaction, of the sphingolipids synthesis and forms 3-ketosphinganine having 18 carbon atoms by condensing serine and palmitoyl-CoA (Barenholz et al., Biochem. Biophys. Acta, 248, 458, 1971; ibid, 306, 341, 1973). 3-ketosphinganine serves as one of long-chain compounds in animals and as a precursor for phytosphingosine in plants and fungi.

In the present invention, the TAPS production can be significantly improved by integrating multiful copies of LCB2 gene into the chromosome of Pichia ciferrii. The transformed Pichia ciferrii cell carrying multiful copies of LCB2 gene on its chromosome produces a large amount of TAPS in a shortened time.

7-1. Isolation of LCB2 Gene Coding for Serine Palmitoyl Transferase

For the purpose of cloning the gene coding for serine palmitoyl transferase from Pichia ciferrii ATCC 14091 genomic DNA, probes were prepared with reference to the subunits of the known serine palmitoyl transferase gene.

Serine palmitoyl transferase coding gene from Saccharomyces cerevisiae consists of two subunits, LCB1 and LCB2. LCB is abbreviation for ‘long chain base.’ (Nagiec et al., Proc. Natl. Aca. Sci. USA, 91, 7899, 1994). DNA sequence of LCB2 genes from other organisms such as human, mouse, Klebsiella lactis, and Schizosaccharomyces pombe (Nagiec et al., Gene, 177, 237, 1996; Hanada et al., J. Biol. Chem., 272, 32108, 1997; Weiss & Stoffel, Eur. J. Biochem., 249, 239, 1997) are reported.

First, by referring the nucleotide sequence of LCB1 gene from Saccharomyces cerevisiae (Nagiec et al., Proc. Natl. Aca. Sci. USA, 91, 7899, 1994), PstI fragment (1 kb) of LCB1 gene was used as probe for Southern blot analysis of genomic DNA of Pichia ciferrii ATCC 14091. In this analysis, no desired band was detected. On the other hand, the Southern blot analysis using SalI fragment (0.9 kb) of LCB2 gene as probe gave DNA band of 12 kb LCB2 gene. This band was collected and inserted into plasmid pBluescript KS+ to give a library. By repeating the Southern blot analysis, ScaI/AflIII fragments (3.0 kb) were obtained and plasmid pL2SA was constructed (FIG. 2). Nucleotide sequence of LCB2 gene was determined and is represented as SEQ. ID. NO. 3 together with its putative amino acid sequence (SEQ. ID. NO. 4) in SEQUENCE LISTING. The sequence was submitted on Mar. 7, 1998 to GenBank under accession number AF053456.

Pichia ciferrii ATCC 14091 LCB2 gene comprises 1688 base pairs and has no intron. The putative amino acid sequence shows a high homology to that from Saccharomyces cerevisiae. Transmembrane helix region is present spanning the 55th-79th amino acids. The region containing lysine, which forms Schiff base together with pyridoxal phosphate, has identical amino acids sequence to those of Saccharomyces cerevisiae.

7-2. Construction of Plasmid prACL2

Plasmid pL2SA was treated with HindIII, Klenow and BamHI, in this order, to give a 3.0 kb fragment of LCB2 gene. This fragment was inserted to plasmid prHEC1.9F, which is treated with Eco47III and BamHI, to give plasmid prACL2.

Plasmid prACL2 has the Pichia ciferrii ribosomal DNA fragment, CYH^(r)(L41) and LCB2 gene, linked to each other, in this order. Plasmid prACL2 was deposited with Korea Collection of Type Cultures in Taejon on May 4, 1998 according to the Budapest Treaty on the International Recognition of the Deposit of Microorganisms for the Purposes of Patent Procedure and given an accession number of KCTC-0468BP.

7-3. Transformation

Plasmid prACL2 was transformed into the mutant Pichia ciferrii KFCC-10937 by following the procedure in the step 5 described above and transformed cells having a high copy number of gene were selected.

7-4. TAPS Production by Transformed Cell Cultivation

The transformed cells obtained in the step 7-3 above were cultivated in YGM optimum medium (glycerol 100 g/liter, yeast extract 2 g/liter, KNO₃ 3 g/liter, (NH₄)₂SO₄ 0.5 g/liter, MgSO₄.7H₂O.0.3 g/liter, NaCl 0.5 g/liter, CSL 3 g/liter and LS-300 1 g/liter) for 4(four) days to produce TAPS.

The transformed cells according to the present invention exhibited TAPS production at least 1.3 times greater than the parent strain KFCC-10937.

8. Isolation of Glyceraldehyde-3-phosphate Dehydrogenase (GAPDH) Promoter Gene From Pichia ciferrii

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is an essential enzyme involved in glycolysis and converts glyceraldehyde-3-phosphate into 1,3-bis-phosphoglycerate. It is a constitutively expressed enzyme. Since GAPDH promoter is hardly affected by carbon source, it attracts the researchers in gene manipulation filed (Kniskem et al., Gene, 46, 135, 1986; Travis et al., J. Biol. Chem., 260, 4384, 1985; Hallewell et al., Biotechnol., 5, 363, 1987; Rosenberg et al., Method Enzymol., 185, 341, 1990; Waterham et al., Gene, 16, 37, 1997).

Based on these studies, the present inventors cloned Pichia ciferrii GAPDH promoter gene and evaluated whether the insertion of GAPDH promoter increases the expression of the desired genes.

8-1. Isolation of GAPDH Gene

GAPDH gene from Saccharomyces cerevisiae 2805 was used to clone GAPDH gene from the genomic DNA of Pichia ciferrii ATCC 14091. By using thus cloned GAPDH gene, plasmid pGH2.2 was constructed (FIG. 4). The nucleotide sequence of GAPDH gene of Pichia ciferrii ATCC 14091 was determined and is represented as SEQ. ID. NO. 5 together with its putative amino acid sequence (SEQ. ID. NO. 6) in SEQUENCE LISTING. This sequence was submitted on Mar. 7, 1998 to GenBank under accession number of AF053300.

Pichia ciferrii ATCC 14091 GAPDH gene comprises 1004 base pairs and has no intron. The nucleotide sequence and the putative amino acid sequence show 69.3% and 76.2% homology to that from Saccharomyces cerevisiae, respectively. This suggests that Pichia ciferrii ATCC 14091 GAPDH gene is new.

8-2. Isolation of GAPDH Promoter Gene

PCR using plasmid pGH2.2 and primers (primer Nos. 3 and 4; SEQ. ID. NO. 9 and SEQ. ID. NO. 10, respectively in SEQUENCE LISTING) was performed to isolate Pichia ciferrii GAPDH promoter gene (600 bp). This gene was inserted into EcoRV site of pT7-Blue T-vector to give plasmid pT7GH.

8-3. Isolation of LCB2 Gene Free of its Own Promoter

LCB2 gene free of its own promoter was isolated from plasmid pL2SA by following the procedure in FIG. 5. The gene has a size of 2.3 kb. It was inserted into BamHI site of pT7GH to give plasmid pGAL2.

8-4. Construction of Plasmid prACGL2

LCB2 gene of 2.9 kb was isolated from plasmid pGAL2 by following the procedure in FIG. 5 and inserted into Eco47III/XbaI site of prHEC1.9F to give plasmid prACGL2.

Plasmid prACGL2 has the Pichia ciferrii ribosomal DNA fragment, CYH^(r)(L41), GAPDH promoter gene and LCB2 gene, linked to each other, in this order. Its restriction map is depicted in FIG. 5. Plasmid prACGL2 was deposited with Korea Collection of Type Cultures in Taejon on Jun. 25, 1998 according to the Budapest Treaty on the International Recognition of the Deposit of Microorganisms for the Purposes of Patent Procedure and given an accession number of KCTC-0498BP.

8-5. Construction of Plasmid prHECGL2

When the host cell (e.g., strain of Pichia ciferrii) is transformed with plasmid prACGL2, the resulting transformed cell will carry genes from Pichia ciferrii as well as other undesired regions of the starting bacterial plasmid since the plasmid is treated with only one restriction enzyme for linearization prior to the transformation into the host cell. To avoid this, the present inventors add Pichia ciferrii ribosomal DNA fragment (800 bp) at the downstream of LCB2 gene of plasmid prACGL2. Thus obtained plasmid was designated as prHECGL2. (FIG. 6)

Plasmid prHECGL2 has the Pichia ciferrii ribosomal DNA fragment, CYH^(r)(L41), GAPDH promoter gene, LCB2 and Pichia ciferrii ribosomal DNA fragment, operably linked to each other, in this order. Its restriction map is depicted in FIG. 6. Plasmid prHECGL2 was deposited with Korea Collection of Type Cultures in Taejon on Aug. 10, 1998 according to the Budapest Treaty on the International Recognition of the Deposit of Microorganisms for the Purposes of Patent Procedure and given an accession number of KCTC-0511BP.

When the host cell is transformed with plasmid prHECGL2, the resulting transformed cell carry only genes from Pichia ciferrii by treating the plasmid by proper restriction enzymes to cut both of the Pichia ciferrii ribosomal DNAs. That is to say, when the plasmid prHECGL2 is transformed into Pichia ciferrii, the obtained transformed cell Pichia ciferrii will carry only endogenous genes.

8-6. Transformation

Cells of Pichia ciferrii KFCC-10937 and plasmid prACL2, prACGL2 and prBECGL2 were mixed, respectively and electroporation was performed at voltage 500V, capacity 50 μF and resistance 800Ω so as to transform the cells with the plasmid.

8-7. TAPS Production by Transformed Cell Cultivation

The transformed cells obtained in the step 8-6 above were cultivated in YGM optimum medium (glycerol 100 g/liter, yeast extract 2 g/liter, KNO₃ 3 g/liter, (NH₄)₂SO₄ 0.5 g/liter, MgSO₄.7H₂O 0.3 g/liter, NaCl 0.5 g/liter, CSL 3 g/liter and LS-300 1 g/liter) to produce TAPS.

The transformed cells with plasmid prACGL2 (KCTC-0498BP) or with plasmid prHECGL2 (KCTC-0511BP) according to the present invention exhibited TAPS production at least 2.1 times and at least 1.5 times greater than the parent strain KFCC-10937 and than the transformed cell with plasmid prACL2 (KCTC-0468BP), respectively.

Free Texts in Sequence Listing

SEQ.ID.NO. 7 is an artificial sequence for PCR primer CYH1.

SEQ.ID.NO. 8 is an artificial sequence for PCR primer CYH4.

SEQ.ID.NO. 9 is an artificial sequence for PCR primer No. 3 which is used for isolation of GAPDH promoter gene.

SEQ.ID.NO. 10 is an artificial sequence for PCR primer No. 4 which is used for isolation of GAPDH promoter gene.

SEQ.ID.NO. 11 is an artificial sequence for PCR primer CH-f

SEQ.ID.NO. 12 is an artificial sequence for PCR primer CH-r.

SEQ.ID.NO. 13 is an artificial sequence for PCR primer 18R.

SEQ.ID.NO. 14 is an artificial sequence for PCR primer 26F.

SEQ.ID.NO. 15 is an artificial sequence for PCR primer L2f.

SEQ.ID.NO. 16 is an artificial sequence for PCR primer L2r.

SEQ.ID.NO. 17 is an artificial sequence for PCR primer No. 1 which is used for isolation of GAPDH gene.

SEQ.ID.NO. 18 is an artificial sequence for PCR primer No. 2 which is used for isolation of GAPDH gene.

EXAMPLES

The present invention will be described in more detail by way of various Examples, which should not be construed to limit the scope of the present invention.

Example 1 Isolation of Genomic DNA from Pichia ciferrii ATCC 14091

Cells of Pichia ciferrii ATCC 14091 grown in YEPD medium (peptone 2%, yeast extract 1% and glucose 2%) by following the method described by Johnston (Johnston et al., Yeast Genetics, molecular aspects, pp. 107-123, IRL Press, 1988) were collected and suspended in SSEM solution (1M sorbitol, 100 mM sodium citrate, 60 mM EDTA, 100 mM 2-mercaptoethanol). Novozyme was added to the suspension to a concentration of 0.1 mg/ml, and allowed to react at 37° C. for 30 minutes to give protoplast. An equal volume of SDS-TE solution (2% SDS, 50 nM EDTA in 1M Tris-Cl, pH 8.0) was added and allowed to react at 60° C. for 10 minutes to disintegrate cells. To the supernatant obtained by centrifuging at 8,000 rpm for 15 minutes, a twice volume of ethanol was added. The resulting pellets were dissolved in TE solution containing RNase to extract Pichia ciferrii genomic DNA.

Example 2 Isolation of L41 Gene From Pichia ciferrii ATCC 14091

Two following primers CYH1 and CYH4 were synthesized.

CYH1: 5′-CGC GTA GTT AAY GTN CCN AAR AC-3′

CYH4: 5′-GCC TGG CCY TTY TGY TTY TTN TC-3′

These two primers are also represented as SEQ. ID. NO. 7 and SEQ. ID. NO. 8, respectively in SEQUENCE LISTING.

PCR was performed using the two primers and Pichia ciferrii genomic DNA obtained in Example 1 to give L41 gene fragment of about 300 bp.

This fragment was labeled with DIG-labeling and detection kit (Boehringer Mannheim) by following the manufacturer's manual to give a probe.

Example 3 Sequencing of L41 Gene

Genomic DNA of Pichia ciferrii obtained in Example 1 was digested with various restriction enzymes, and the digestion products were subjected to 0.9% agarose gel electrophoresis and transferred to Nytran^(R) membrane (Schleicher & Schuell) followed by hybridization with a hybridization solution (5×SSC, 0.1% N-laurylsarcosine, 0.02% SDS, 2% blocking agent and 30% formaldehyde) using probes obtained in Example 2. The hybridization was carried out at 42° C. for 6 hours according to the manufacturer's manual prepared by Boehringer Mannheims.

Antibodies coupled to alkaline phosphatase were introduced and BCIP and X-phosphate were added. Violet-stained band was observed.

Band is detected at 1.9 kb size of genomic DNA treated with EcoRI. This DNA fragment (1.9 kb) was collected and linked to EcoRI site of plasmid pBluescript KS+ (Stratagene) and transformed into E. coli DH5α to establish a library.

This library was repeatedly subjected to Southern blot analysis to isolate 1.9 kb gene fragment containing L41 gene(plasmid pCYH1.9). Nucleotide sequencing was performed for this plasmid using Automatic sequencer Model 373A (Applied Biosystem). The result is represented as SEQ. ID. NO. 1 together with its putative amino acid sequence (SEQ. ID. NO. 2) in SEQUENCE LISTING. This sequence was submitted on Mar. 7, 1998 to GenBank under accession number of AF053457.

L41 gene of Pichia ciferrii ATCC 14091 consists of 737 base pairs including 419 bp intron. The amino acid residue 56 is proline.

Example 4 Construction of Plasmid PCYH1.9^(r) in Which Proline (aa 56) is Replaced by Glutamine

Two primers CH-f and CH-r were prepared:

Primer CH-f: GGT CAA ACC AAA CCA GTT TTC

Primer CH-r: ATG GAA AAC TTG TTT GGT TTG ACC

These two primers are also represented as SEQ ID. NO. 11 and SEQ. ID. NO. 12, respectively in SEQUENCE LISTING.

Combinations of universal primer and primer CH-r, and of reverse primer and primer CH-f were employed for PCR using Pfu DNA polymerase and pCYH1.9 as a template to obtain two PCR products of 1.2 kb and 0.7 kb.

PCR was performed again using the two PCR products (1.2 kb and 0.7 kb), and universal and reverse primers to obtain plasmid PCYH1.9^(r) in which proline (aa 56) is replaced by glutamine.

Example 5 Construction of Plasmid prDX9.0 Containing Ribosomal DNA Fragment

Two following primers 18R and 26F were synthesized.

Primer 18R: 5′-CAA TAA TTG CAA TGC TCT ATC CCC AGC ACG-3′

Primer 26F: 5′-GGA TAT GGA TTC TTC ACG GTA ACG TAA CTG-3′

These two primers are also represented as SEQ. ID. NO. 13 and SEQ. ID. NO. 14, respectively in SEQUENCE LISTING.

PCR was performed using the two primers and Pichia ciferrii genomic DNA obtained in Example 1 to give a PCR product of 6.0 kb. This PCR product was labeled in the same manner as in Example 2 to give a probe.

When the probe is subjected to Southern blot analysis with Pichia ciferrii genormic DNA, band is detected at 9 kb size of genomuic DNA treated with XhoI. This DNA fragment (9 kb) was collected and inserted into plasmid pBluescript KS+ (Stratagene) and its library was established. This library was repeatedly subjected to Southern blot analysis to isolate 9 kb gene fragment containing ribosomal DNA (plasmid prDX9.0).

Nucleotide sequencing was performed for this plasmid using Automatic sequencer Model 373A (Applied Biosystem). The results including the location and orientation of 26S, 18S, 5.8S and 5S ribosomal gene are shown in FIG. 1.

Example 6 Construction of Plasmid prXHNC

Plasmid prDX9.0 obtained in Example 5 was treated with XbaI to obtain 3.5 kb ribosomal DNA, which is then inserted into plasmid pBluescript KS+. The resulting recombinant plasmid is treated with HpaI/NcoI/Klenow to remove 1.6 kb ribosomal DNA and linked to 1.9 kb CYH^(r) gene, which was obtained by digesting plasmid pCYH1.9^(r) in Example 4 with EcoRI/Klenow, to obtain plasmid prXHC.

Example 7 Construction of Plasmid prEHC

Plasmid prDX9.0 obtained in Example 5 was treated with EcoRI to obtain 3.8 kb ribosomal DNA, which is then inserted into plasmid pbluescript KS+. The resulting recombinant plasmid is treated with HpaI to remove 2 kb ribosomal DNA and Linked to 1.9 kb CYH^(r) gene, which was obtained by digesting plasmid pCYH1.9^(r) in Example 4 with EcoRI/Klenow, to obtain plasmid prEHC.

Example 8 Construction of Plasmid prCEX

Plasmid prDX9.0 obtained in Example 5 was treated with EcoRI/XbaI to obtain 1. 1 kb ribosomal DNA. 1.9 kb CYH^(r) gene, which was obtained by digesting plasmid pCYH1.9^(r) in Example 4with EcoRI/Klenow, was linked to EcoRI site of the 1.1 kb ribosomal DNA to give plasmid prCEX.

Example 9 Construction of Plasmid prCRX

Plasmid prDX9.0 obtained in Example 5 was treated with EcoRV/XbaI to obtain 1.3 kb ribosomal DNA. 1.9 kb CYH^(r) gene, which was obtained by digesting plasmid pCYH1.9^(r) in Example 4 with EcoRI/Klenow, was lined to EcoRV site of the 1.3 kb ribosomal DNA to give plasmid prCRX.

Example 10 Construction of Plasmid prXCH

Plasmid prDX9.0 obtained in Example 5 was treated with XbaI to obtain 3.5 kb ribosomal DNA. 1.9 kb CYH^(r) gene, which was obtained by digesting plasmid PCYH1.9^(r) in Example 4 with EcoRI/Klenow, was linked to HpaI site of the 3.5 kb ribosomal DNA to give plasmid prXCH.

Example 11 Construction of Plasmid prXCE

Plasmid prDX9.0 obtained in Example 5 was treated with XbaI to obtain 3.5 kb ribosomal DNA. 1.9 kb CYH^(r) gene, which was obtained by digesting plasmid pCYH1.9^(r) in Example 4 with EcoRI, was linked to EcoRI site of the 3.5 kb ribosomal DNA to give plasmid prXCE.

Example 12 Construction of Plasmid prXHC1.9

Plasmid prDX9.0 obtained in Example 5 was treated with XhoI/HindIII to obtain 1.6 kb ribosomal DNA. A plasmid containing this 1.6 kb ribosomal DNA was digested with HindIII/Klenow to give ribosomal DNA. 1.9 kb CYH^(r) gene, which was obtained by digesting plasmid pCYH1.9^(r) in Example 4 with EcoRI, was linked to EcoRI site of the HindIII/Klenow digestion product to give plasmid prXHC1.9.

Example 13 Construction of Plasmid prAC1.9

Plasmid prDX9.0 obtained in Example 5 was treated with HindIII/EcoRV to obtain 0.6 kb ribosomal DNA. 1.9 kb CYH^(r) gene, which was obtained by digesting plasmid pCYH1.9^(r) in Example 4 with EcoRI/Klenow, was linked to EcoRV site of the 0.6 kb ribosomal DNA to give plasmid prAC1.9.

Example 14 Construction of Plasmid prEC1.9

Plasmid prDX9.0 obtained in Example 5 was treated with HindIII/EcoRI to obtain 1.4 kb ribosomal DNA. 1.9 kb CYH^(r) gene, which was obtained by digesting plasmid pCYH1.9^(r) in Example 4 with EcoRI, was linked to EcoRI site of the 1.4 kb ribosomal DNA to give plasmid prXCH.

Example 15 Construction of Plasmid prHEC1.9F

Plasmid prDX9.0 obtained in Example 5 was treated with HindIII/EcoRI to obtain 1.4 kb ribosomal DNA. 1.9 kb CYH^(r) gene, which was obtained by digesting plasmid pCYH1.9^(r) in Example 4 with EcoRI/Klenow, was linked to EcoRV site of the 1.4 kb ribosomal DNA to give plasmid prHEC1.9F.

Example 16 Construction of Plasmid prHEC1.9R

The procedure in Example 15 was repeated except that the insertion orientation of CYH^(r) was opposite to that of Example 5 to obtain plasmid prHEC1.9R.

Example 17 Transformation Efficiency of Plasmids

The method described by Klass and Peter (Klass & Peter, Curr. Genet., 25, 305, 1994) was followed. That is to say, cells of Pichia ciferrii KFCC-10937 grown in YEPD medium (100 ml) to OD_(600 nm) of 1.5 were collected by centrifugation and dispersed in 50 mM phosphate buffer (pH 7.5; 40 ml), to which 25 mM DTT was added, at 37° C. for 15 minutes. The mixture was washed twice with ice-cooled stabilization solution (100 ml; 270 mM sucrose, 10 mM Tris-Cl (pH 7.5), 1 mM MgCl₂) and suspended in 1 ml of stabilization solution.

To the resulting suspension (50 microliters), 5 microliters of the solution of respective plasmids obtained in Examples 6-16 are added and allowed to stand on ice for 10 minutes. Then, the solution was transferred to 0.2 mm electroporation cuvettes (Bio-Rad). Electroporation was carried out using Gene-pulser II (Bio-Rad) at 500V, 50 μF and 800Ω, and the electroporation product was suspended into 0.5 mL of stabilization solution. After adding 2 mL of YEPD medium, the cultivation was carried out at 25° C. for 5 hours. Then the culture broth was plated on YEPD solid medium, to which 10 μg/mL of cycloheximide was added, at 25° C. for 4-5 days. The number of transformed cells was counted and transformation efficiency was shown in Table 2.

TABLE 2 No. of transformed No. of transformed Plasmid cell per μg Plasmid cell per μg prXHNC 276 prEHC 250 prCEX 194 prCRX 226 prXCH 314 prXCE 134 prAC1.9 1574 prXHC1.9 1287 prEC1.9 983 prHC1.9F 1760 prHEC1.9R 54

The results in Table 2 reveals that the site of ribosomal DNA where CYH^(r) gene is inserted and the transcription direction of CYH^(r) gene are closely related with the transformation efficiency. Plasmids prAC1.9 and prHEC1.9F in which the non-transcribed region between 5S and 26S ribosomal RNA structural genes is used as an insertion site has the highest transformation efficiency. And, prHEC1.9R in which the transcription direction of 5S RNA gene is opposite to that of CYH^(r) shows significantly decreased transformation efficiency.

Based on these results, plasmid prHEC1.9F was selected.

Example 18 Selection of Transformation Conditions

In order to establish the optimum conditions of transformation, linear prHEC1.9 obtained after treating with ApaI/ScaI was transformed by following the procedure in Example 17 except that the voltage was changed to 500, 600 or 700V and the resistance to 100, 200, 300, 400, 500, 600, 700 or 800Ω while keeping the capcity of 50 μF. The results are shown in Table 3.

TABLE 3 Voltage (V) Resistance (Ω) No. of transformed cell per μg 500 100 0 200 82 300 1065 400 1770 500 2890 600 4250 700 6300 800 6850 600 100 0 200 210 300 1488 400 2644 500 5250 600 6750 700 6500 800 4740 700 100 18 200 620 300 2360 400 4400 500 3840 600 2640

The results in Table 3 confirm that the optimum transformation conditions are capacity 50 μF, voltage 500V and resistance 800Ω.

Example 19 Analysis of Transformed Cell by Southern Blot Analysis

Each of transformed cells selected in Example 17 was inoculated into YEPD medium to which 5 μg/mL of cycloheximide was added and subjected to cultivation while agitation at 25° C. for 18-20 hours, followed by centrifugation to collect cell pellets. Thus obtained cells were placed in 1.5 mL tubes. Cells were suspended in 30 μL of STES solution (0.5M NaCl, 0.01M EDTA, 1% SDS in 0.2M Tris-Cl, pH 7.6) and 0.8 volumes of glass beads (diameter 0.4 mm) were added thereto. The mixtures were stirred for 5 minutes, 200 μL of TE buffer (1 mM EDTA in 10 mM Tris-Cl, pH 8.0) and 200 μL of phenol/chloroform/isoamylalcohol (25:24:1) were added. The resulting mixtures were stirred for 2 minutes and centrifuged at 12,000 rpm. 2.5 Volumes of ethanol was added to the supernatant to precipitate genomic DNA and dried.

Genomic DNA (2-3 μg) was dissolved into 50 ∞L of distilled water, treated with EcoRI, and subjected to electrophoresis on 0.8% agarose gel. Southern blot analysis was carried out by using L41 gene in Example 2 as a probe to detect bands. It was observed that 4-5 copies of L41 gene are carried on genomic DNA of all transformed cells.

Example 20 Construction of Plasmid prACL2

(1) Isolation of LCB2 Gene From Pichia ciferrii ATCC 14091.

Cells of Saccharomyces cerevisiae grown in YEPD medium (peptone 2%, yeast extract 1% and glucose 2%) by following the method described by Johnston (Johnston et al., Yeast Genetics, molecular aspects, pp.107-123, IRL Press, 1988) were collected and genomic DNA was isolated therefrom.

Two following primers L2f and L2r were synthesized.

Primer L2f: 5′-ATG AGT ACT CCT GCA AAC TA-3′

Primer L2r: 5′-TAA CAM AAT ACT TGT CGT CC-3′

These two primers are also represented as SEQ. ID. NO. 15 and SEQ. ID. NO. 16, respectively in SEQUENCE LISTING.

PCR was performed using the two primers and the Saccharomyces cerevisiae genomic DNA obtained in the above to give LCB2 gene fragment of about 1680 bp. The SalI fragment of 913bp was labeled with DIG-labeling and detection kit (Boehringer Mannheim) by following the manufacturer's manual to give a probe.

Genomic DNA of Pichia ciferrii obtained in Example 1 was digested with various restriction enzymes, BamHI, EcoRI, EcoRV, HindIII, PstI or SalI, and the digestion products were subjected to electrophoresis in TAE buffer and transferred to Nytran^(R) membrane (Sckleicher & Schuell) followed by Southern blot analysis.

The Southern blot analysis was carried out using a hybridization solution (5×SSC, 0.1% N-laurylsarcosine, 0.02% SDS, 2% blocking agent and 30% formamide) at 42° C. for 6 hours according to the manufacturer's manual prepared by Boehringer Mannheims.

Antibodies coupled to alkaline phosphatase were introduced and BCIP and X-phosphate were added. Violet color-stained bands were observed.

Band is detected at 12 kb size of genomic DNA treated with HindIII.

This DNA fragment(12kb) was collected and inserted into plasmid pBluescript KS+ (Stratagene) and transformed into E. coli DH5α to establish a library.

This library was repeatedly subjected to Southern blot analysis to isolate 3.0 kb SacI/AflIII fragment containing LCB2 gene(plasmid pL2SA).

Restriction map and sequencing of Pichia ciferrii LCB2 gene are shown in FIG. 2. The nucleotide sequence is represented as SEQ. ID. NO. 3 together with its putative amino acid sequence (SEQ. ID. NO. 4) in SEQUENCE LISTING. The nucleotide sequence was submitted on Mar. 7, 1998 to GenBank under accession number of AF053456.

LCB2 gene of Pichia ciferrii ATCC 14091 consists of 1688 base pairs without intron, and its putative amino acid sequence shows a high homology to that of Saccharomyces cerevisiae.

(2) Construction of Plasmid prACL2

Plasmid prHEC1.9F obtained in Example 15 was digested with Eco47III/BamHI to give a linear one. On the other hand, plasmid pL2SA obtained in (1) above was treated with HindIII, Klenow and BamHI, in this order, to give a 3.0 kb fragment of LCB2 gene. This 3.0 kb fragment was inserted to the above linear plasmid to give plasmid prACL2. (FIG. 3)

Plasmid prACL2 has the Pichia ciferrii ribosomal DNA fragment, CYH^(r)(L41) and LCB2 gene, linked to each other, in this order. Plasmid prACL2 was deposited with Korea Collection of Type Cultures in Taejon on May 4, 1998 according to the Budapest Treaty on the International Recognition of the Deposit of Microorganisms for the Purposes of Patent Procedure and given an accession number of KCTC-0468BP.

Example 21 Transformation

Plasmid prACL2 was linearized with ApaI and transformed into the mutant Pichia ciferrii KFCC-10937 by following the procedure in Example 17. 10²-10³ colonies per μg of plasmid were formed. Twelve largest colonies were selected.

Each of transformed cells was inoculated into YEPD medium to which 5 μg/mL of cycloheximide was added and subjected to cultivation while agitation at 25° C. for 18-20 hours, followed by centrifugation to collect cell pellets.Thus obtained cells were placed in 1.5 mL tubes. Cells were suspended in 30 μL of STES solution (0.5M NaCl, 0.01M EDTA, 1% SDS in 0.2M Tris-Cl, pH 7.6) and 0.8 volumes of glass beads (diameter 0.4 mm) were added thereto. The mixtures were stirred for 5 minutes, 200 μL of TE buffer (1 mM EDTA in 10 mM Tris-Cl, pH 8.0) and 200 μL of phenol/chloroform/isoamylalcohol (25:24:1) were added. The resulting mixtures were stirred for 2 minutes and centrifuged at 12,000 rpm. 2.5 Volumes of ethanol was added to the supernatant to precipitate genomic DNA and dried.

Genomic DNA (2-3 μg) was dissolved into 50 μL of distilled water, treated with EcoRI, and subjected to electrophoresis on 0.8% agarose gel. Southern blot analysis was carried out by using L41 gene in Example 2 as a probe to detect bands. It was observed that 5-10 copies of L41 gene are carried on genomic DNA of all transformed cells. One of them is picked up and named as ‘Transformed cell 1.’

Comparative Example 1 TAPS Production by Strain KFCC-10937 Cultivation

The parent strain KFCC-10937 was cultivated in 100 ML of YGM optimum medium (glycerol 100 g/liter, yeast extract 2 g/liter, KNO₃ 3 g/liter, (NH₄)₂SO₄ 0.5 g/liter, MgSO₄.7H₂O 0.3 g/liter, NaCl 0.5 g/liter, CSL 3 g/liter and LS-300 1 g/liter) at 25° C. and 250 rpm for 4 days. After standing at 25° C. for 2 days, 4 volumes of mixed solvent of chloroform/methanol (1:1) was added to separate phases and extract TAPS.

TAPS was analyzed on HPLC using ELSD(Electron Light Scanning Detector). As solvent, a mixture of iso-octane and THF/formic acid (100:1.5) varying its ratio 9:1, 7:3 and then 9:1 was used.

Example 22 TAPS Production by Transformed Cell 1

Transformed cell 1 obtained in Example 20 was cultivated in the same condition and manner as in Comparative Example 1 to produce TAPS.

TAPS productions in Comparative Example 1 and Example 22 are shown in Table 4.

TABLE 4 Transformed KFCC-10937 cell 1 Doubling Time (hr) 1.5 1.5 Biomass concentration (g/L) 41.6 43.6 Amount of TAPS (mg/L) 5206 7444 TAPS specific yield (mg/gdw*) 125.1 170.7 Volume productivity (mg TAPS/L/hr) 54.2 77.5 *gdw = dry weight (g)

The results in Table 4 affirmed that the transformation of Pichia ciferrii with the expression cassette according to the present invention makes it possible to maximize the integration of the desired gene onto the chromosome of the host.

Example 23 Preparation of Probe for GAPDH Gene Cloning

Two following primers (Primer No. 1 and No. 2) were synthesized.

Primer 1: 5′-ATG GTT AGA GTT GCT ATT AAC G-3′

Primer 2: 5′-AAG CCT TGG CAA TGT GTT CAA-3′

These two primers also represented as SEQ. ID. NO. 17 and SEQ. ID. NO. 18, respectively in SEQUENCE LISTING.

PCR was performed using the two primers to isolate 1 kb GAPDH gene from Saccharomyces cerevisiae 2805 (provided by courtesy of R. B. Wickner at NIH). The gene was inserted into EcoRV site of plasmid pT7-Blue T-vector (Novagen) to obtain plasmid pT7-SGH.

Plasmid pT7-SGH was digested with XbaI and SalI to give 0.9 kb gene fragment, which was labeled with DIG-labeling and detection kit (Boehringer Mannheim) by following the manufacturer's manual to give a probe.

Example 24 Isolation of GAPDH Gene from Pichia ciferrii

Genomic DNA of Pichia ciferrii obtained in Example 1 was digested with various restriction enzymes, BamHI, EcoRI, EcoRV, HindIII, PstI or SalI, and the digestion products were subjected to electrophoresis on 0.9% agarose gel and transferred to Nytran^(R) membrane (Schleicher & Schuell) followed by Southern blot analysis using the probe obtained in Example 23.

The Southern blot analysis was carried out using a hybridization solution (5×SSC, 0.1% N-laurylsarcosine, 0.02% SDS, 2% blocking agent and 30% formamide) at 42° C. for 6 hours according to the manufacturer's manual prepared by Boehringer Mannheim.

Antibodies coupled to alkaline phosphatase were introduced and BCIP and X-phosphate were added. Violet color-stained bands were observed at about 6 kb sized fragment of the genomic DNA treated with HindIII/EcoRI.

This DNA fragment (about 6 kb) was collected and inserted into plasmid pBluescript KS+ (Stratagene) and transformed into E. coli DH5α to establish a library. This library was repeatedly subjected to Southern blot analysis to isolate 6.0 kb AflIII/HindIII fragment containing GAPDH gene(plasmid pGH2.2).

The restriction map and sequencing of GAPDH gene of Pichia ciferrii ATCC 14091 are shown in FIG. 4. The nucleotide sequence is represented as SEQ. ID. NO. 5 together with its putative amino acid sequence (SEQ. ID. NO. 6) in SEQUENCE LISTING. This sequence was submitted on Mar. 7, 1998 to GenBank under accession number of AF053300.

Pichia ciferrii ATCC 14091 GAPDH gene comprises 1004 base pairs and has no intron. The nucleotide sequence and the putative amino acid sequence show 69.3% and 76.2% homology to that from Saccharomyces cerevisiae, respectively.

Example 25 Isolation of Pichia ciferrii GAPDH Promoter Gene

Two following primers (Primer No. 3 and No. 4) were synthesized.

Primer 3: 5′-GAT ATC TAC ATA CAA TTG ACC CAT AG-3′

Primer 4: 5′-GGA TCC TTA ATT ATT TGT TTG TTT-3′

These two primers are also represented as SEQ. ID. NO. 9 and SEQ. ID. NO. 10, respectively in SEQUENCE LISTING.

PCR using plasmid pGH2.2 obtained in Example 24 and the two primers (primer Nos. 3 and 4) was performed to isolate Pichia ciferrii GAPDH promoter gene (600 bp). This gene was inserted into EcoRV site of pT7-Blue T-vector to give plasmid pT7GH.

Example 26 Isolation of LCB2 Gene Free of its Own Promoter

Plasmid pL2SA obtained in Example 20 was treated with AflIII to give promoter-free LCB2 gene (2.3 kb). This 2.3 kb gene was treated with Klenow and inserted into plasmid pBluescript KS+ treated with BamHI/Klenow to give plasmid pL2B2.3. (FIG. 5)

Plasmid pL2B2.3 was digested with BamHI to give 2.3 kb LCB2 gene, which was inserted to BamHI site of plasmid pT7GH in Example 4 to give pGAL2.

Example 27 Construction of Exression Cassette

Plasmid prHEC1.9F obtained in Example 15 was linearized by treating with Eco47III and XbaI. GAPDH promoter/LCB2 gene (2.9 kb) obtained by treating plasmid pGAL2 (Example 26) with EcoRV and XbaI was inserted to the linear plasmid prHEC1.9F to give prACGL2. (FIG. 5)

Plasmid prACGL2 has the Pichia ciferrii ribosomal DNA fragment, CYH^(r)(L41), GAPDH promoter gene and LCB2 gene, linked to each other, in this order. Plasmid prACGL2 was deposited with Korea Collection of Type Cultures in Taejon on Jun. 25, 1998 according to the Budapest Treaty on the International Recognition of the Deposit of Microorganisms for the Purposes of Patent Procedure and given an accession number of KCTC-0498BP.

Plasmid pCYH1.9^(r) obtained in Example 4 was linearized by treating with Eco47III and XbaI. GAPDH promoter/LCB2 gene (2.9 kb) obtained by treating plasmid pGAL2 (Example 26) with EcoRV and XbaI was inserted to the linear plasmid pCYH1.9^(r) to give pCHGL2. (FIG. 6). This plasmid was treated with EcoRV/XbaI/Klenow to give 4.6 kb CYH^(r)/GAPDH promoter/LCB2 gene which is then inserted to EcoRV site of 1.4 kb ribosomal DNA, which was obtained by treating plasmid prDX9.0 (Example 5) with HindIII/EcoRI, to give plasmid prHECGL2. (FIG. 6)

Plasmid prHECGL2 has a structure that it contains additional Pichia ciferrii ribosomal DNA fragment (800 bp) linked at downstream of LCB2 gene of plasmid prACGL2. That is to say, plasmid prHECGL2 contains Pichia ciferrii ribosomal DNA fragment, CYH^(r)(L41), GAPDH promoter gene, LCB2 and Pichia ciferrii ribosomal DNA fragment, operatively linked to each other, in this order.

Plasmid prHECGL2 was deposited with Korea Collection of Type Cultures in Taejon on Aug. 10, 1998 according to the Budapest Treaty on the International Recognition of the Deposit of Microorganisms for the Purposes of Patent Procedure and given an accession number of KCTC-0511BP.

Plasmid prHECGL2 is distinguished from and advantagous over plasmid prACGL2 that the former introduces only Pichia ciferrii endogenous genes onto the chromosome of Pichia ciferrii transformed cell while the latter introduces Pichia ciferrii endogenous genes together with bacterial genes (originated from plasmid pBluescript KS+) when they are used to transform Pichia ciferrii.

Example 28 Transformation

Plasmid prACGL2 (Example 27) and prHECGL2 (Example 27) were linearized with ApaI and ApaI/ScaI, respectively. Then, these linear plasmids were transformed into Pichia ciferrii KFCC-10937 by following the procedure in Example 17. 10³ colonies per μg of plasmid were formed. Four largest colonies were selected for respective plasmid-transformed cells.

Each of transformed cells was inoculated into YEPD medium to which 5 μg/mL of cycloheximide was added and subjected to cultivation while agitation at 25° C. for 18-20 hours, followed by centrifugation to collect cell pellets. Thus obtained cells were placed in 1.5 mL tubes. Cells were suspended in 30 μL of STES solution (0.5M NaCl, 0.01M EDTA, 1% SDS in 0.2M Tris-Cl, pH 7.6) and 0.8 volumes of glass beads (diameter 0.4 mm) were added thereto. The mixtures were stirred for 5 minutes, 200 μL of TE buffer (1 mM EDTA in 10 mM Tris-Cl, pH 8.0) and 200 μL of phenol/chloroform/isoamylalcohol (25:24:1) were added. The resulting mixtures were stirred for 2 minutes and centrifuged at 12,000 rpm. Two and half (2.5) volumes of ethanol was added to the supernatant to precipitate genomic DNA and dried.

Genomic DNA (2-3 μg) was dissolved into 50 μL of distilled water, treated with HindIII, EcoRI or XbaI, and subjected to electrophoresis on 0.8% agarose gel. Southern blot analysis was carried out by using DIG-labeled L41 gene, DIG-labeled LCB2 gene or DIG-labeled GAPDH promoter gene as a probe to detect bands (FIGS. 7A-7D). It was observed that about 4-5 copies of the genes are carried on genomic DNA of all transformed cells. Each one of the respective prACGL2-transformed and prHECGL2-transformed cells is picked up and named as ‘Transformed cell 2’ and ‘Transformed cell 3,’ respectively.

Example 29 TAPS Production by Transformed Cell 2

Transformed cell 2 obtained in Example 28 was cultivated in the same condition and manner as in Comparative Example 1 to produce TAPS. TAPS production is shown in Table 5.

TABLE 5 Transformed cell 2 (prACGL2) Doubling Time (hr) 1.5 Biomass concentration (g/L) 40.1 Amount of TAPS (mg/L) 10933 TAPS specific yield (mg/gdw*) 272.6 Volume productivity (mg TAPS/L/hr) 113.9 *gdw = dry weight (g).

Example 30 and Comparative Example 2 TAPS Production by Transformed Cell 3

Transformed cell 2 obtained in Example 28 or parent strain of Pichia ciferrii was cultivated in YMGL medium (yeast extract 3 g/L, malt extract 3 g/L, glycerol 30 g/L) under the same conditions as that in Comparative Example 1 to produce TAPS. TAPS productions are shown in Table 6.

TABLE 6 Parent Strain Transformed cell 3 (KFCC-10937) (prHECGL2) TAPS in mg/mL 0.200 0.420 TAPS in g/g cell 0.012 0.027

The results in Table 6 reveal that the absolute production of TAPS in YMGL medium decreases when compared to that in YGM optimum medium, and that the TAPS production by transformed cell 3 is 2.1 times greater than that of the parent strain.

In summary, the present invention has following advantages:

(1) The expression cassette of the present invention allows a maximized integration of desired genes into chromosome of host Pichia ciferrii cells.

(2) Plasmid prACL2 according to the present invention has 0.6 kb Pichia ciferrii ribosomal DNA fragment, CYH^(r)(L41) and LCB2 gene coding for serine palmitoyl transferase, operatively linked to each other, in this order. It shows a good efficiency of transformation into host cells and the resulting transformed cells show at least 1.3 times greater TAPS production than the parent strain.

(3) Introduction of GAPDH promoter gene into the expression cassette according to the present invention allows a further increase in the expression of the desired gene in the transformed cell.

(4) Plasmid prACGL2 according to the present invention has 0.6 kb Pichia ciferrii ribosomal DNA fragment, CYH^(r)(L41), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) promoter gene and LCB2 gene, and plasmid prHECGL2 has further Pichia ciferrii ribosomal DNA fragment of 800 bp at the downstream of the LCB2 gene in plasmid prACGL2. These plasmids show an excellent transformation efficiency as well as show TAPS production at least 2.1 times greater than the parent strain KFCC-10937 due to an increased expression of LCB2 gene by action of GAPDH promoter.

Although preferred embodiments of the present invention have been described in detail herein above, it should be clearly understood that many variations and/or modifications of the basic inventive concepts herein taught which may appear to those skilled in the art will still fall within the spirit and scope of the present invention as defined in the appended claims.

<160> NUMBER OF SEQ ID NOS: 18 <210> SEQ ID NO 1 <211> LENGTH: 1906 <212> TYPE: DNA <213> ORGANISM: Pichia ciferrii <220> FEATURE: <221> NAME/KEY: CDS <222> LOCATION: (603)..(605) <221> NAME/KEY: CDS <222> LOCATION: (1025)..(1348) <221> NAME/KEY: intron <222> LOCATION: (606)..(1024) <400> SEQUENCE: 1 gaattctctt aaatgatgtt ggattaaaaa ccttgatcct ttctcttgaa t #ataaatata     60 tcactttcaa accagttgaa tatgtgaagt agtttggttg ttgatgtagt t #taaatctgt    120 attctatttt tggtgtagat ctgtatatgt caattacttt tttttttcct c #gtacaattt    180 caagtttaca aacaagtgga aatgtaaaca accacgcgtt tcaaaaaaaa a #gttctgttc    240 tagatctaag acacctagtc aggtgatatt aagctagggc tatatgattg a #tgtttgctc    300 aaaagatgtg actgtctgga aatgaaaatt ctagcagtgg tgttcagatg t #tcttgcacc    360 aaccaacaaa ctctgaacaa ttcgcgaagc aaacaacact aacacacgtg a #ttatgtcat    420 caattcatga tcttttctct tagatttcgc gattcaagcc agagtggtgt t #tgggttggg    480 cacttttttt ttctgtattc gcagagactc agtgttggtt tttcaaaagt g #ttgaaattt    540 aatactcttt ttgtagtagt tattatagag accatcatta aaaggtacaa c #atcagttaa    600 aa atg ggtatgtcca tatgaagtta agatacaaga ggatcagtgt at #gagtagag        655    Met      1 aatcacaatc atgtcaatgt tgttatttga atcgttgtca aaagtgtaat t #ttgtttgtt    715 caatgttgaa atttataatt tgaaagattt aagcaaagtt caaggggcaa a #agaataaag    775 aatacaagag taatgaaaga ttaaagaagt aatacaagct attgagagaa g #attcattca    835 gatatagtta agatcacaag tgacagaagt tttaaatgat ttcagtaatt t #ttaatccat    895 attcataacc tacaaagtta agatgatcaa acaatattga gaataaagat a #caaatgtat    955 tcaaaccact caactatcct acttgaatcc aaaatctatg atttgaataa t #atactaaca   1015 agaactata gtc aac gtt cca aaa acc aga aaa ac #c tac tgt aaa ggt aaa   1066           Val Asn Val Pro Lys # Thr Arg Lys Thr Tyr Cys Lys Gly Lys                    #      5             #      10             #      15 gag tgt aga aaa cac act caa cac aaa gtt a #cc caa tac aaa gct ggt     1114 Glu Cys Arg Lys His Thr Gln His Lys Val T #hr Gln Tyr Lys Ala Gly                  20  #                 25  #                 30 aaa gct tct tta ttt gct caa ggt aaa cgt c #gt tat gac cgt aaa caa     1162 Lys Ala Ser Leu Phe Ala Gln Gly Lys Arg A #rg Tyr Asp Arg Lys Gln              35      #             40      #             45 tcc ggt tac ggt ggt caa acc aaa cca gtt t #tc cat aaa aaa gct aaa     1210 Ser Gly Tyr Gly Gly Gln Thr Lys Pro Val P #he His Lys Lys Ala Lys          50          #         55          #         60 act acc aaa aaa gtt gtt tta cgt tta gaa t #gt gtt gtt tgt aaa acc     1258 Thr Thr Lys Lys Val Val Leu Arg Leu Glu C #ys Val Val Cys Lys Thr      65              #     70              #     75 aaa gct caa tta tca tta aaa cgt tgt aaa c #at ttc gaa tta ggt ggt     1306 Lys Ala Gln Leu Ser Leu Lys Arg Cys Lys H #is Phe Glu Leu Gly Gly  80                  # 85                  # 90                  # 95 gac aga aaa caa aaa ggt caa gct tta caa t #tc taa ggt ggt             # 1348 Asp Arg Lys Gln Lys Gly Gln Ala Leu Gln P #he     Gly Gly                 100  #                105 taaattattt gattattttg cactactatt aaaggggggt ttgtatatct t #aatgtaacg   1408 ttttacagat aaagattgat gtagtgggaa gtgtcctgtc tatcaaggcc t #atatagact   1468 tttgactatt attttcgtag taatactacc tagatagtag atgagtctag t #tgtagttcc   1528 cttcgtatgt gattcattca gcctaattaa aatcctttca aatcgccctc g #caattttta   1588 agtgtccctt cagatttgaa attagaacca aaatttctga atctgttttt g #aaagggacc   1648 ataaaaagtt agtggtttca agatcaaaat caaaatcaaa atcaacttta g #cgctgaatc   1708 aaatcaacaa caaccatcag tggcgttcaa cacatcacca agggcgtcaa a #ccagggcaa   1768 aacagtacag gaaagaccac agaaacacac agaatccata ggaaccacag g #aagcaccat   1828 cacattcccc aagagcgcat tcattcccgt tgaaatcaag ctacataccc a #aatagacag   1888 atcaaaacat tggaattc              #                   #                   #1906 <210> SEQ ID NO 2 <211> LENGTH: 106 <212> TYPE: PRT <213> ORGANISM: Pichia ciferrii <400> SEQUENCE: 2 Met Val Asn Val Pro Lys Thr Arg Lys Thr T #yr Cys Lys Gly Lys Glu   1               5  #                 10  #                 15 Cys Arg Lys His Thr Gln His Lys Val Thr G #ln Tyr Lys Ala Gly Lys              20      #             25      #             30 Ala Ser Leu Phe Ala Gln Gly Lys Arg Arg T #yr Asp Arg Lys Gln Ser          35          #         40          #         45 Gly Tyr Gly Gly Gln Thr Lys Pro Val Phe H #is Lys Lys Ala Lys Thr      50              #     55              #     60 Thr Lys Lys Val Val Leu Arg Leu Glu Cys V #al Val Cys Lys Thr Lys  65                  # 70                  # 75                  # 80 Ala Gln Leu Ser Leu Lys Arg Cys Lys His P #he Glu Leu Gly Gly Asp                  85  #                 90  #                 95 Arg Lys Gln Lys Gly Gln Ala Leu Gln Phe             100      #            105 <210> SEQ ID NO 3 <211> LENGTH: 3296 <212> TYPE: DNA <213> ORGANISM: Pichia ciferrii <220> FEATURE: <221> NAME/KEY: CDS <222> LOCATION: (765)..(2453) <400> SEQUENCE: 3 acttgatgaa taggaatggt ataaagaaaa acatgacaaa taagtaggaa g #tagcagcaa     60 ctgaacctaa tgattctgga ataacaggtt tattgggttt ggataaatct t #taccatata    120 gacctatctt gatgaatgat gaagataatt ttgggattaa ataatttgtt g #atatgaatc    180 caattaaact gaatcctaaa gcagcttgta atggttcagt tatcccatag g #aaccttggg    240 aagtgtatat tattgttatg gctattccta ggagggatag ttctggaagg g #acattgtgt    300 gattgacgta gcatgtgtaa tcaattggtg atgatattga tattgtattg a #tctaatagt    360 gtatagattg tttattgata tttatttgtt tacgtgtctg cttatgttat g #tgttatgta    420 atacttaata ggagaattta taataggggt ataatgagaa gaataaaaga a #taatgaaga    480 atatgatcaa caaagaattg aattgaatga gaataaaata ataataatat a #ataaaagaa    540 caataaaaga acaatataaa taataatata atcatcttat cattcaatta c #caaccactt    600 attaatcctt gcttcgttca attcttctca aacgcgaatt caaacaagaa c #aagtgaatt    660 tcaaatttaa acaaacaaac aaaactataa aaacaatcaa atatccagaa a #acagacaac    720 caaccaacca ataccaatac caataccaat agaactatac caac atg  #tca ttg gta     776                    #                   #             Met Ser Leu  #Val                    #                   #               1 ata cct caa ata gat cta tca ggt ctt tcc a #tc gaa gac aag aaa caa      824 Ile Pro Gln Ile Asp Leu Ser Gly Leu Ser I #le Glu Asp Lys Lys Gln   5                 #  10                 #  15                 #  20 aat gaa ttc ggt gct cta act tca aat gaa t #at cgt tac aaa aca att      872 Asn Glu Phe Gly Ala Leu Thr Ser Asn Glu T #yr Arg Tyr Lys Thr Ile                  25  #                 30  #                 35 tca aga cag ggg aaa cca tta cct gat cca a #tt gaa gat gaa cca cca      920 Ser Arg Gln Gly Lys Pro Leu Pro Asp Pro I #le Glu Asp Glu Pro Pro              40      #             45      #             50 tat cat gtc ctt ttc atc act tat tta aac t #at tta atc ttg att atc      968 Tyr His Val Leu Phe Ile Thr Tyr Leu Asn T #yr Leu Ile Leu Ile Ile          55          #         60          #         65 gtt ggt cat att aaa gat ttc aca ggt att c #tg ttc aac cca aaa aat     1016 Val Gly His Ile Lys Asp Phe Thr Gly Ile L #eu Phe Asn Pro Lys Asn      70              #     75              #     80 tac caa gat tta tta gaa caa aat ggc ctt g #ct cca tgg tat aat aaa     1064 Tyr Gln Asp Leu Leu Glu Gln Asn Gly Leu A #la Pro Trp Tyr Asn Lys  85                  # 90                  # 95                  #100 ttt gaa agt ttt tat att cgt cgt atg aaa c #aa aaa att gat gat tgt     1112 Phe Glu Ser Phe Tyr Ile Arg Arg Met Lys G #ln Lys Ile Asp Asp Cys                 105  #                110  #                115 ttt gca aga cca act tgt ggt gtc cca ggt a #ga tta atc act tgt att     1160 Phe Ala Arg Pro Thr Cys Gly Val Pro Gly A #rg Leu Ile Thr Cys Ile             120      #            125      #            130 gat cgt gat gct cat gat tat aat tca tat t #tt agt tat cct ggt act     1208 Asp Arg Asp Ala His Asp Tyr Asn Ser Tyr P #he Ser Tyr Pro Gly Thr         135          #        140          #        145 act tca act tgt tta aat tta tca tca tat a #at tat ttg ggg ttt gca     1256 Thr Ser Thr Cys Leu Asn Leu Ser Ser Tyr A #sn Tyr Leu Gly Phe Ala     150              #    155              #    160 caa tct gaa ggg gca tgt act caa gcc gct t #ta gaa att ttg gat tat     1304 Gln Ser Glu Gly Ala Cys Thr Gln Ala Ala L #eu Glu Ile Leu Asp Tyr 165                  #170                  #175                  #180 tat ggt gtt ggt tct ggt ggt cca aga aat g #tt att ggt act act gat     1352 Tyr Gly Val Gly Ser Gly Gly Pro Arg Asn V #al Ile Gly Thr Thr Asp                 185  #                190  #                195 tta cat tta aaa act gaa aaa act ata gca a #aa ttt att ggt aaa gat     1400 Leu His Leu Lys Thr Glu Lys Thr Ile Ala L #ys Phe Ile Gly Lys Asp             200      #            205      #            210 gat tca atc tta ttt tca atg ggg tat gca a #ca aat gca agt tta ttt     1448 Asp Ser Ile Leu Phe Ser Met Gly Tyr Ala T #hr Asn Ala Ser Leu Phe         215          #        220          #        225 agt tct tta ttg gat aag aaa tca ctt gtt a #tt tct gat gaa tta aat     1496 Ser Ser Leu Leu Asp Lys Lys Ser Leu Val I #le Ser Asp Glu Leu Asn     230              #    235              #    240 cat gct tca att aga act ggt gtt aga tta t #ct ggt tct aca gtt aaa     1544 His Ala Ser Ile Arg Thr Gly Val Arg Leu S #er Gly Ser Thr Val Lys 245                  #250                  #255                  #260 act ttc cct cat aat aat atg att gcc ttg g #aa aaa att ctt aga gaa     1592 Thr Phe Pro His Asn Asn Met Ile Ala Leu G #lu Lys Ile Leu Arg Glu                 265  #                270  #                275 caa att tct caa ggt caa cca aga tct cat c #gt cca tgg aaa aaa atc     1640 Gln Ile Ser Gln Gly Gln Pro Arg Ser His A #rg Pro Trp Lys Lys Ile             280      #            285      #            290 att gtt gca gtt gaa ggg ctt tat tca atg g #ag ggt aca atg gca aat     1688 Ile Val Ala Val Glu Gly Leu Tyr Ser Met G #lu Gly Thr Met Ala Asn         295          #        300          #        305 tta cct gca tta att gaa tta aga aga aaa t #at aaa ttt aat tta ttt     1736 Leu Pro Ala Leu Ile Glu Leu Arg Arg Lys T #yr Lys Phe Asn Leu Phe     310              #    315              #    320 gtt gat gaa gct cat tca att ggt gct att g #gt cca tca ggt cgt ggt     1784 Val Asp Glu Ala His Ser Ile Gly Ala Ile G #ly Pro Ser Gly Arg Gly 325                  #330                  #335                  #340 gtt tgt gat tat ttt ggt ata gat ccc tca a #at gtt gat tta tta atg     1832 Val Cys Asp Tyr Phe Gly Ile Asp Pro Ser A #sn Val Asp Leu Leu Met                 345  #                350  #                355 ggg act tta act aaa tca ttt ggt gct gca g #gt ggt tat att gct ggt     1880 Gly Thr Leu Thr Lys Ser Phe Gly Ala Ala G #ly Gly Tyr Ile Ala Gly             360      #            365      #            370 tca caa caa att ata aat cgt tta aaa tta a #at att aat tca caa aat     1928 Ser Gln Gln Ile Ile Asn Arg Leu Lys Leu A #sn Ile Asn Ser Gln Asn         375          #        380          #        385 tat gca gaa tct atc cct gca cct gtt ttg g #ca caa att att tct tcg     1976 Tyr Ala Glu Ser Ile Pro Ala Pro Val Leu A #la Gln Ile Ile Ser Ser     390              #    395              #    400 tta aat atc atc tcg ggt gat tta aat cct g #gt gaa ggt tcg gaa aga     2024 Leu Asn Ile Ile Ser Gly Asp Leu Asn Pro G #ly Glu Gly Ser Glu Arg 405                  #410                  #415                  #420 tta gaa aga att gct ttt aat tca cgt tat t #ta aga tta ggt tta caa     2072 Leu Glu Arg Ile Ala Phe Asn Ser Arg Tyr L #eu Arg Leu Gly Leu Gln                 425  #                430  #                435 aga tta ggt ttt atc gta tac gga gtt gat g #at tca cca gtg atc cca     2120 Arg Leu Gly Phe Ile Val Tyr Gly Val Asp A #sp Ser Pro Val Ile Pro             440      #            445      #            450 tta tta tta ttc gcc cca gcc aaa atg cca g #ca ttt tca cgt atg cta     2168 Leu Leu Leu Phe Ala Pro Ala Lys Met Pro A #la Phe Ser Arg Met Leu         455          #        460          #        465 tat caa gga aaa att tca gtt gtt gtt gtt g #ga tac ccg gca act cca     2216 Tyr Gln Gly Lys Ile Ser Val Val Val Val G #ly Tyr Pro Ala Thr Pro     470              #    475              #    480 ctg act tca tca gga gtt cgt ctt ggt gtt c #ct gca tct tta cca aag     2264 Leu Thr Ser Ser Gly Val Arg Leu Gly Val P #ro Ala Ser Leu Pro Lys 485                  #490                  #495                  #500 gag gat atg gat tat ctt tta cgt cat tta t #cc gag ttg ggt gat aaa     2312 Glu Asp Met Asp Tyr Leu Leu Arg His Leu S #er Glu Leu Gly Asp Lys                 505  #                510  #                515 tta ttt tta aaa ttt agt tct ggt att gct g #gt ggt tct tta gat ggt     2360 Leu Phe Leu Lys Phe Ser Ser Gly Ile Ala G #ly Gly Ser Leu Asp Gly             520      #            525      #            530 tca cca cca aga tgg aat att gaa gat gtt t #tg aaa gag act cca aag     2408 Ser Pro Pro Arg Trp Asn Ile Glu Asp Val L #eu Lys Glu Thr Pro Lys         535          #        540          #        545 gat tgt aaa gaa tct aaa tat ttt att gca a #ct gca aat aat tga         2453 Asp Cys Lys Glu Ser Lys Tyr Phe Ile Ala T #hr Ala Asn Asn     550              #    555              #    560 taaataattg atttataatt ttaatagcta atttaataat ttaataataa t #atacaacat   2513 ctatatgatc ttttttggtg taatttatag cttatcatct tatcatctta t #ataatcgga   2573 atgttacaat gtaatagaaa agaatgaaaa aaaaccctta caatctgaaa a #aaaagataa   2633 agatcataaa tatgcaaatt attgtttaaa atatttcttt caaaccctta t #tatgatctt   2693 ttgaattcaa gtaattataa ttccttcttt cttgatcaaa ttatttccat t #ttttgtgta   2753 gttgatgata caaatttttc atttttgatc ttcatttttt tcaacattgc c #ataattttt   2813 tgaataccac caaaataaaa aataaaaaaa aaataaacac ggaaaaatta a #aatcaaaac   2873 atttcaaaac attgttggtg aaaggtatac taaagatcag gttcagatat t #agttattag   2933 gtattaccag gtttctcatc ataggttaag aattaggaga atacattact a #ggatctgat   2993 tgttgagttg ataattggtg gtagttacgt gttgctcatt tggtatagat c #tcaattata   3053 cattcttttg aaaaggtgtt gataatactt tgagaatact ttgaaattat t #caaatttat   3113 agaggttcat atcattacta cattgttgat tattacaagt ttgtgtggtt t #tttgaattc   3173 tcatccattc ctttatttta acactttata catatttgac atatccaatt a #ttaccatag   3233 cattccatag catattcatc atagcatatc atattcatag caggtcattt c #aattatgaa   3293 ttc                  #                   #                   #            3296 <210> SEQ ID NO 4 <211> LENGTH: 562 <212> TYPE: PRT <213> ORGANISM: Pichia ciferrii <400> SEQUENCE: 4 Met Ser Leu Val Ile Pro Gln Ile Asp Leu S #er Gly Leu Ser Ile Glu   1               5  #                 10  #                 15 Asp Lys Lys Gln Asn Glu Phe Gly Ala Leu T #hr Ser Asn Glu Tyr Arg              20      #             25      #             30 Tyr Lys Thr Ile Ser Arg Gln Gly Lys Pro L #eu Pro Asp Pro Ile Glu          35          #         40          #         45 Asp Glu Pro Pro Tyr His Val Leu Phe Ile T #hr Tyr Leu Asn Tyr Leu      50              #     55              #     60 Ile Leu Ile Ile Val Gly His Ile Lys Asp P #he Thr Gly Ile Leu Phe  65                  # 70                  # 75                  # 80 Asn Pro Lys Asn Tyr Gln Asp Leu Leu Glu G #ln Asn Gly Leu Ala Pro                  85  #                 90  #                 95 Trp Tyr Asn Lys Phe Glu Ser Phe Tyr Ile A #rg Arg Met Lys Gln Lys             100      #            105      #            110 Ile Asp Asp Cys Phe Ala Arg Pro Thr Cys G #ly Val Pro Gly Arg Leu         115          #        120          #        125 Ile Thr Cys Ile Asp Arg Asp Ala His Asp T #yr Asn Ser Tyr Phe Ser     130              #    135              #    140 Tyr Pro Gly Thr Thr Ser Thr Cys Leu Asn L #eu Ser Ser Tyr Asn Tyr 145                  #150                  #155                  #160 Leu Gly Phe Ala Gln Ser Glu Gly Ala Cys T #hr Gln Ala Ala Leu Glu                 165  #                170  #                175 Ile Leu Asp Tyr Tyr Gly Val Gly Ser Gly G #ly Pro Arg Asn Val Ile             180      #            185      #            190 Gly Thr Thr Asp Leu His Leu Lys Thr Glu L #ys Thr Ile Ala Lys Phe         195          #        200          #        205 Ile Gly Lys Asp Asp Ser Ile Leu Phe Ser M #et Gly Tyr Ala Thr Asn     210              #    215              #    220 Ala Ser Leu Phe Ser Ser Leu Leu Asp Lys L #ys Ser Leu Val Ile Ser 225                  #230                  #235                  #240 Asp Glu Leu Asn His Ala Ser Ile Arg Thr G #ly Val Arg Leu Ser Gly                 245  #                250  #                255 Ser Thr Val Lys Thr Phe Pro His Asn Asn M #et Ile Ala Leu Glu Lys             260      #            265      #            270 Ile Leu Arg Glu Gln Ile Ser Gln Gly Gln P #ro Arg Ser His Arg Pro         275          #        280          #        285 Trp Lys Lys Ile Ile Val Ala Val Glu Gly L #eu Tyr Ser Met Glu Gly     290              #    295              #    300 Thr Met Ala Asn Leu Pro Ala Leu Ile Glu L #eu Arg Arg Lys Tyr Lys 305                  #310                  #315                  #320 Phe Asn Leu Phe Val Asp Glu Ala His Ser I #le Gly Ala Ile Gly Pro                 325  #                330  #                335 Ser Gly Arg Gly Val Cys Asp Tyr Phe Gly I #le Asp Pro Ser Asn Val             340      #            345      #            350 Asp Leu Leu Met Gly Thr Leu Thr Lys Ser P #he Gly Ala Ala Gly Gly         355          #        360          #        365 Tyr Ile Ala Gly Ser Gln Gln Ile Ile Asn A #rg Leu Lys Leu Asn Ile     370              #    375              #    380 Asn Ser Gln Asn Tyr Ala Glu Ser Ile Pro A #la Pro Val Leu Ala Gln 385                  #390                  #395                  #400 Ile Ile Ser Ser Leu Asn Ile Ile Ser Gly A #sp Leu Asn Pro Gly Glu                 405  #                410  #                415 Gly Ser Glu Arg Leu Glu Arg Ile Ala Phe A #sn Ser Arg Tyr Leu Arg             420      #            425      #            430 Leu Gly Leu Gln Arg Leu Gly Phe Ile Val T #yr Gly Val Asp Asp Ser         435          #        440          #        445 Pro Val Ile Pro Leu Leu Leu Phe Ala Pro A #la Lys Met Pro Ala Phe     450              #    455              #    460 Ser Arg Met Leu Tyr Gln Gly Lys Ile Ser V #al Val Val Val Gly Tyr 465                  #470                  #475                  #480 Pro Ala Thr Pro Leu Thr Ser Ser Gly Val A #rg Leu Gly Val Pro Ala                 485  #                490  #                495 Ser Leu Pro Lys Glu Asp Met Asp Tyr Leu L #eu Arg His Leu Ser Glu             500      #            505      #            510 Leu Gly Asp Lys Leu Phe Leu Lys Phe Ser S #er Gly Ile Ala Gly Gly         515          #        520          #        525 Ser Leu Asp Gly Ser Pro Pro Arg Trp Asn I #le Glu Asp Val Leu Lys     530              #    535              #    540 Glu Thr Pro Lys Asp Cys Lys Glu Ser Lys T #yr Phe Ile Ala Thr Ala 545                  #550                  #555                  #560 Asn Asn <210> SEQ ID NO 5 <211> LENGTH: 1928 <212> TYPE: DNA <213> ORGANISM: Pichia ciferrii <220> FEATURE: <221> NAME/KEY: CDS <222> LOCATION: (907)..(1911) <221> NAME/KEY: promoter <222> LOCATION: (1)..(906) <400> SEQUENCE: 5 gttgataatt tataattgat aatgatttaa acttttgatt ataaattgat t #aaaacccat     60 gtcatctagt atataataac aatgaccata actataataa ttagtaccca t #caattacta    120 ataccataac atactatacc atataccata atatactata gtctatacgt c #tataccata    180 tattataaca ttgtatttcc taatcaaact ttcatctgat gttttatcaa c #ctttgtaaa    240 ctttgatcaa ctgtttgtct gtttgtcaac tgatgattgg aaccacatga t #tatatgcaa    300 agcaataaaa caacaaacaa caacaacttt acccagtggt acctacatac a #attgaccca    360 tagtaaacta ataactcata acacaataaa gcatctgatc ttaatgtact a #ctaaatact    420 aaactgatga taattacttt tgttgtaatg tttgtcatca ctttgatcat c #acgagcatc    480 accggaccgt taattaccaa caatctcaat tgtacaacat agtgttaaaa c #aggataact    540 tgatgattat atgtgatatt aagttcaaac aagtaccaat aaatagataa t #taatagctc    600 tataatatat catttaattg aattaatatc aatagttgtt gtttaattat c #cctagtttt    660 ctggttaaag ttacaccatc agatggttca ccaccaatgt tgttcaaacc a #tttccactc    720 aactgacgtt tccagaacat caccctgaaa aaaaaaaatt catcacacat t #gggagaaat    780 tggggaggat tgtatataag gagtggaaat tcgctaatat ttttataatt c #taactcact    840 tgttttaatt caacatcagt attttataat acaaaaacaa acaaacaaac a #aataattaa    900 ttaaca atg gct atc aca gtt ggt att aac ggt  #ttc ggt cgt att ggt       948        Met Ala Ile Thr Val Gly I #le Asn Gly Phe Gly Arg Ile Gly          1          #      5             #      10 cgt tta gtc cta aga att gct ctt tca aga a #aa gat att caa att gtt      996 Arg Leu Val Leu Arg Ile Ala Leu Ser Arg L #ys Asp Ile Gln Ile Val  15                  # 20                  # 25                  # 30 gca att aat gat cca ttc att gca cca gaa t #at gct tca tat atg ttt     1044 Ala Ile Asn Asp Pro Phe Ile Ala Pro Glu T #yr Ala Ser Tyr Met Phe                  35  #                 40  #                 45 aaa tat gat tct act cat ggt cgt tat tca g #gt gaa gtt tct cat gaa     1092 Lys Tyr Asp Ser Thr His Gly Arg Tyr Ser G #ly Glu Val Ser His Glu              50      #             55      #             60 ggt gaa aac att gtt att gat ggt aaa aaa a #tc aga gtt tat caa gaa     1140 Gly Glu Asn Ile Val Ile Asp Gly Lys Lys I #le Arg Val Tyr Gln Glu          65          #         70          #         75 cgt gat cca gtt aat atc cca tgg ggt aaa g #at ggt gtt gat tat gtt     1188 Arg Asp Pro Val Asn Ile Pro Trp Gly Lys A #sp Gly Val Asp Tyr Val      80              #     85              #     90 att gat tca act ggt gtt ttt aaa gaa tta g #at tct gct caa aaa cat     1236 Ile Asp Ser Thr Gly Val Phe Lys Glu Leu A #sp Ser Ala Gln Lys His  95                  #100                  #105                  #110 att gat gcc ggt gct aaa aaa gtt gtt att a #ct gct cca tca tca act     1284 Ile Asp Ala Gly Ala Lys Lys Val Val Ile T #hr Ala Pro Ser Ser Thr                 115  #                120  #                125 gct cca atg ttt gtt gtt ggt gtt aat gaa g #at aaa tat act cca gat     1332 Ala Pro Met Phe Val Val Gly Val Asn Glu A #sp Lys Tyr Thr Pro Asp             130      #            135      #            140 tta aac att att tca aat gct tca tgt aca a #ca aat tgt tta gct cca     1380 Leu Asn Ile Ile Ser Asn Ala Ser Cys Thr T #hr Asn Cys Leu Ala Pro         145          #        150          #        155 tta gct aaa att att aac aat aaa ttt ggt a #tt gaa gaa ggt tta atg     1428 Leu Ala Lys Ile Ile Asn Asn Lys Phe Gly I #le Glu Glu Gly Leu Met     160              #    165              #    170 act act gtt cat tca att act gct act caa a #aa act gtt gat ggt cca     1476 Thr Thr Val His Ser Ile Thr Ala Thr Gln L #ys Thr Val Asp Gly Pro 175                  #180                  #185                  #190 tct cat aaa gat tgg aga agt ggt cct act g #ct tca ggt aat att att     1524 Ser His Lys Asp Trp Arg Ser Gly Pro Thr A #la Ser Gly Asn Ile Ile                 195  #                200  #                205 cca tca tca act ggt gct gct aaa gct gtt g #gt aaa gtt att cca gaa     1572 Pro Ser Ser Thr Gly Ala Ala Lys Ala Val G #ly Lys Val Ile Pro Glu             210      #            215      #            220 ttg gct ggt aaa tta act ggt atg tct tta a #ga gtt cca act gtt gat     1620 Leu Ala Gly Lys Leu Thr Gly Met Ser Leu A #rg Val Pro Thr Val Asp         225          #        230          #        235 gtt tca gtt gtt gat tta act gtt aaa tta t #ta aaa gat gcc act tat     1668 Val Ser Val Val Asp Leu Thr Val Lys Leu L #eu Lys Asp Ala Thr Tyr     240              #    245              #    250 gat gaa att aaa gct gct gtt aaa gaa gct g #ct gaa ggt cca tta aaa     1716 Asp Glu Ile Lys Ala Ala Val Lys Glu Ala A #la Glu Gly Pro Leu Lys 255                  #260                  #265                  #270 ggt gtt gtt ggt tat act gaa gat caa gtt g #tt tct tca gat ttc tta     1764 Gly Val Val Gly Tyr Thr Glu Asp Gln Val V #al Ser Ser Asp Phe Leu                 275  #                280  #                285 act gat aac aga tca tca att ttt gat gct g #aa gct ggt att tgg tta     1812 Thr Asp Asn Arg Ser Ser Ile Phe Asp Ala G #lu Ala Gly Ile Trp Leu             290      #            295      #            300 tca cca aga ttt gtt aaa tta att gct tgg t #at gat aat gaa tat ggt     1860 Ser Pro Arg Phe Val Lys Leu Ile Ala Trp T #yr Asp Asn Glu Tyr Gly         305          #        310          #        315 tac tct acc aga gtt gtt gat tta tta gaa t #ac gtt gct tca aag aac     1908 Tyr Ser Thr Arg Val Val Asp Leu Leu Glu T #yr Val Ala Ser Lys Asn     320              #    325              #    330 taa gagtagaacg aaagctt            #                   #                 192 #8 <210> SEQ ID NO 6 <211> LENGTH: 334 <212> TYPE: PRT <213> ORGANISM: Pichia ciferrii <400> SEQUENCE: 6 Met Ala Ile Thr Val Gly Ile Asn Gly Phe G #ly Arg Ile Gly Arg Leu   1               5  #                 10  #                 15 Val Leu Arg Ile Ala Leu Ser Arg Lys Asp I #le Gln Ile Val Ala Ile              20      #             25      #             30 Asn Asp Pro Phe Ile Ala Pro Glu Tyr Ala S #er Tyr Met Phe Lys Tyr          35          #         40          #         45 Asp Ser Thr His Gly Arg Tyr Ser Gly Glu V #al Ser His Glu Gly Glu      50              #     55              #     60 Asn Ile Val Ile Asp Gly Lys Lys Ile Arg V #al Tyr Gln Glu Arg Asp  65                  # 70                  # 75                  # 80 Pro Val Asn Ile Pro Trp Gly Lys Asp Gly V #al Asp Tyr Val Ile Asp                  85  #                 90  #                 95 Ser Thr Gly Val Phe Lys Glu Leu Asp Ser A #la Gln Lys His Ile Asp             100      #            105      #            110 Ala Gly Ala Lys Lys Val Val Ile Thr Ala P #ro Ser Ser Thr Ala Pro         115          #        120          #        125 Met Phe Val Val Gly Val Asn Glu Asp Lys T #yr Thr Pro Asp Leu Asn     130              #    135              #    140 Ile Ile Ser Asn Ala Ser Cys Thr Thr Asn C #ys Leu Ala Pro Leu Ala 145                  #150                  #155                  #160 Lys Ile Ile Asn Asn Lys Phe Gly Ile Glu G #lu Gly Leu Met Thr Thr                 165  #                170  #                175 Val His Ser Ile Thr Ala Thr Gln Lys Thr V #al Asp Gly Pro Ser His             180      #            185      #            190 Lys Asp Trp Arg Ser Gly Pro Thr Ala Ser G #ly Asn Ile Ile Pro Ser         195          #        200          #        205 Ser Thr Gly Ala Ala Lys Ala Val Gly Lys V #al Ile Pro Glu Leu Ala     210              #    215              #    220 Gly Lys Leu Thr Gly Met Ser Leu Arg Val P #ro Thr Val Asp Val Ser 225                  #230                  #235                  #240 Val Val Asp Leu Thr Val Lys Leu Leu Lys A #sp Ala Thr Tyr Asp Glu                 245  #                250  #                255 Ile Lys Ala Ala Val Lys Glu Ala Ala Glu G #ly Pro Leu Lys Gly Val             260      #            265      #            270 Val Gly Tyr Thr Glu Asp Gln Val Val Ser S #er Asp Phe Leu Thr Asp         275          #        280          #        285 Asn Arg Ser Ser Ile Phe Asp Ala Glu Ala G #ly Ile Trp Leu Ser Pro     290              #    295              #    300 Arg Phe Val Lys Leu Ile Ala Trp Tyr Asp A #sn Glu Tyr Gly Tyr Ser 305                  #310                  #315                  #320 Thr Arg Val Val Asp Leu Leu Glu Tyr Val A #la Ser Lys Asn                 325  #                330 <210> SEQ ID NO 7 <211> LENGTH: 23 <212> TYPE: DNA <213> ORGANISM: Artificial Sequence <220> FEATURE: <223> OTHER INFORMATION: Description of Artificial # Sequence: PCR primer       CYH1 <221> NAME/KEY: unsure <222> LOCATION: (15) <223> OTHER INFORMATION: n is A, C, G, T  #or known base analogue <221> NAME/KEY: unsure <222> LOCATION: (18) <223> OTHER INFORMATION: n is A, C, G, T  #or known base analogue <400> SEQUENCE: 7 cgcgtagtta aygtnccnaa rac           #                   #                 23 <210> SEQ ID NO 8 <211> LENGTH: 23 <212> TYPE: DNA <213> ORGANISM: Artificial Sequence <220> FEATURE: <223> OTHER INFORMATION: Description of Artificial # Sequence: PCR primer       CYH4 <221> NAME/KEY: unsure <222> LOCATION: (21) <223> OTHER INFORMATION: n is A, C, G, T  #or known base analogue <400> SEQUENCE: 8 gcctggccyt tytgyttytt ntc           #                   #                 23 <210> SEQ ID NO 9 <211> LENGTH: 26 <212> TYPE: DNA <213> ORGANISM: Artificial Sequence <220> FEATURE: <223> OTHER INFORMATION: Description of Artificial # Sequence: PCR primer       No. 3 which  is used for i #solation of GAPDH promoter gene <400> SEQUENCE: 9 gatatctaca tacaattgac ccatag           #                   #              26 <210> SEQ ID NO 10 <211> LENGTH: 24 <212> TYPE: DNA <213> ORGANISM: Artificial Sequence <220> FEATURE: <223> OTHER INFORMATION: Description of Artificial # Sequence: PCR primer       No. 4 which  is used for i #solation of GAPDH promoter gene <400> SEQUENCE: 10 ggatccttaa ttatttgttt gttt           #                   #                24 <210> SEQ ID NO 11 <211> LENGTH: 21 <212> TYPE: DNA <213> ORGANISM: Artificial Sequence <220> FEATURE: <223> OTHER INFORMATION: Description of Artificial # Sequence: PCR primer       CH-f <400> SEQUENCE: 11 ggtcaaacca aaccagtttt c            #                   #                   #21 <210> SEQ ID NO 12 <211> LENGTH: 24 <212> TYPE: DNA <213> ORGANISM: Artificial Sequence <220> FEATURE: <223> OTHER INFORMATION: Description of Artificial # Sequence: PCR primer       CH-r <400> SEQUENCE: 12 atggaaaact tgtttggttt gacc           #                   #                24 <210> SEQ ID NO 13 <211> LENGTH: 30 <212> TYPE: DNA <213> ORGANISM: Artificial Sequence <220> FEATURE: <223> OTHER INFORMATION: Description of Artificial # Sequence: PCR primer       18R <400> SEQUENCE: 13 caataattgc aatgctctat ccccagcacg          #                   #           30 <210> SEQ ID NO 14 <211> LENGTH: 30 <212> TYPE: DNA <213> ORGANISM: Artificial Sequence <220> FEATURE: <223> OTHER INFORMATION: Description of Artificial # Sequence:  PCR primer       26F <400> SEQUENCE: 14 ggatatggat tcttcacggt aacgtaactg          #                   #           30 <210> SEQ ID NO 15 <211> LENGTH: 20 <212> TYPE: DNA <213> ORGANISM: Artificial Sequence <220> FEATURE: <223> OTHER INFORMATION: Description of Artificial # Sequence:  PCR primer       L2f <400> SEQUENCE: 15 atgagtactc ctgcaaacta             #                   #                   # 20 <210> SEQ ID NO 16 <211> LENGTH: 20 <212> TYPE: DNA <213> ORGANISM: Artificial Sequence <220> FEATURE: <223> OTHER INFORMATION: Description of Artificial # Sequence: PCR primer       L2r <400> SEQUENCE: 16 taacaaaata cttgtcgtcc             #                   #                   # 20 <210> SEQ ID NO 17 <211> LENGTH: 22 <212> TYPE: DNA <213> ORGANISM: Artificial Sequence <220> FEATURE: <223> OTHER INFORMATION: Description of Artificial # Sequence: PCR primer       No. 1 which is used for isola #tion of GADPH gene <400> SEQUENCE: 17 atggttagag ttgctattaa cg            #                   #                 22 <210> SEQ ID NO 18 <211> LENGTH: 21 <212> TYPE: DNA <213> ORGANISM: Artificial Sequence <220> FEATURE: <223> OTHER INFORMATION: Description of Artificial # Sequence:  PCR primer       No. 2 which is used for isola #tion of GADPH gene <400> SEQUENCE: 18 aagccttggc aatgtgttca a            #                   #                   #21 

What is claimed is:
 1. An isolated L41 gene represented as SEQ ID NO: 1 and coding for a Pichia ciferrii ribosomal protein.
 2. An expression cassette for Pichia ciferrii comprising: (a) a Pichia ciferrii ribosomal DNA, which is operably linked to (b) a modified L41 gene of SEQ ID NO: 1, wherein its encoded amino acid proline at residue 56 is replaced with glutamine, and (c) a desired structural gene, said modified L41 gene being operably linked to said desired structural gene.
 3. The expression cassette according to claim 2, wherein said Pichia ciferrii ribosomal DNA is a non-transcribed region comprising the about 1.4 kb fragment of HindIII/EcoRI digestion product thereof.
 4. The expression cassette according to claim 2, wherein said desired structural gene is the LCB2 gene coding for Pichia ciferrii serine palmitoyl transferase and represented as SEQ ID NO:
 3. 5. The expression cassette according to claim 3, wherein said desired structural gene is the LCB2 gene coding for Pichia ciferrii serine palmitoyl transferase and represented as SEQ ID NO:
 3. 6. A plasmid comprising the expression cassette according to claim 5 which is plasmid prACL2 (KCTC-0496BP) having the restriction map in FIG.
 3. 7. A process for producing a protein product coded by a desired structural gene comprising the step of transforming a Pichia ciferrii cell with a plasmid having the expression cassette of claim 2, wherein the protein product is expressed in said Pichia ciferrii cell.
 8. The process according to claim 7, wherein Pichia ciferrii is transformed by electroporation under conditions of the voltage of about 500V, the capacity of about 50 μF, and the resistance of about 800Ω.
 9. A Pichia ciferrii cell transformed with a vector comprising the expression cassette of claim
 2. 10. A Pichia ciferrii cell transformed with a vector comprising the expression cassette of claim
 3. 11. A Pichia ciferrii cell transformed with a vector comprising the expression cassette of claim
 4. 12. A Pichia ciferrii cell transformed with a vector comprising the expression cassette of claim
 5. 13. A Pichia ciferrii cell transformed with a vector comprising the expression cassette of claim
 6. 14. A process for producing tetraacetyl phytosphingosine comprising the steps of (a) cultivating the transformed Pichia ciferrii cell of claim 11 in a suitable cultivation medium; and (b) recovering tetraacetyl phytosphingosine therefrom.
 15. A process for producing tetraacetyl phytosphingosine comprising the steps of (a) cultivating the transformed Pichia ciferrii cell of claim 12 in a suitable cultivation medium; and (b) recovering tetraacetyl phytosphingosine therefrom.
 16. A process for producing tetraacetyl phytosphingosine comprising the steps of (a) cultivating the transformed Pichia ciferrii cell of claim 13 in a suitable cultivation medium; and (b) recovering tetraacetyl phytosphingosine therefrom.
 17. An isolated LCB2 gene represented as SEQ ID NO: 3 and coding for Pichia ciferrii serine palmitoyl transferase.
 18. An expression cassette for Pichia ciferrii comprising: (a) a Pichia ciferrii ribosomal DNA, which is operably linked to (b) a modified L41 gene encoding for the polypeptide consisting of amino acid residues of SEQ ID NO: 2, wherein its encoded amino acid proline at residue 56 is replaced with glutamine, and (c) a desired structural gene, said modified L41 gene being operably linked to said desired structural gene. 